Machining apparatus having a light signal display device, and method

ABSTRACT

Machining apparatus (2), in particular wide-belt sander for machining preferably board-type workpieces (W) preferably made at least in part of wood, engineered wood and/or plastic, comprising at least one light signal display device (10) which displays information on the machining apparatus (2) in such a way that the information displayed by the light signal display device (10) is visible to an operator.

FIELD OF THE INVENTION

The invention relates to a machining apparatus, in particular wide-belt sander, for machining preferably panel-shaped workpieces, as well as a method.

PRIOR ART

In the field of machining apparatus, in particular machining apparatus used in the craft sector, workpiece handling is almost entirely up to the operator of the machining apparatus, and this can result in that the tool of the machining apparatus is not evenly worn over the engaging time of the tool. Engaging time is understood as being that time during which the tool was already engaged. Uneven wear of the tool can be an obstacle to a consistent surface quality of the workpieces to be machined.

Moreover, partial (one-sided) wear of a tool can even accelerate wear of the tool and at worst result in damage to the tool and probably to the workpiece currently being machined.

It is generally known, for example in wide-belt sanders as a specific example of a machining apparatus, that the individual workpieces to be machined often do no occupy the entire width of the wide-belt sander. The result of this is that during machining of such a workpiece only a certain part of the abrasive (abrasive belt) is used and thus becomes worn, with the remaining part of the abrasive being unused. This leads to the necessity that the operator distributes over the entire engaging time of the abrasive (abrasive belt), the workpieces to be machined over the entire width of the wide-belt sander such that the abrasive is approximately evenly worn.

For example, DE 199 26 946 A1, which relates to an apparatus for pneumatic position control of a workpiece with regard to a predetermined workpiece arrangement in a workpiece mount, discloses as auxiliary means an LED display indicating by colored identification of the fields whether the workpiece has been correctly inserted into the workpiece mount.

Moreover, for example, DE 20 2011 101 666 U1 is known as prior art, which describes a plate machining system with a control device and a light signal device signally coupled thereto, the light signal device comprising a plurality of LEDs. By a corresponding control of the LEDs, it is possible to indicate to an operator an area in which a workpiece should be placed. The current position of a saw aggregate belonging to the distributor can also be displayed.

DESCRIPTION OF THE INVENTION

It is therefore the object of the present invention to provide a machining apparatus, in particular a wide-belt sander, for machining preferably plate-shaped workpieces, with which a substantially consistent, high machining quality is ensured.

The object is solved by a machining apparatus according to claim 1 as well as a method according to claim 14.

Preferred further developments of the invention are indicated in the dependent claims. Features of the dependent device and method claims can each be used in the independent claims. For example, a control device of the machining apparatus can be configured or adapted to carry out certain method steps.

One of the central ideas of the present invention is to visually display to an operator of the machining apparatus by a light signal display device a wear condition of a tool of the machining apparatus and/or an advantageous insertion position of the workpiece to be machined in the machining apparatus.

By means of the proposed light signal display device, it is therefore possible in a simple and safe way to constantly display to an operator of the machining apparatus the current wear condition of a tool and/or an advantageous insertion position of a workpiece to be machined by the machining apparatus. Thus, the operator can be provided with means which enable the operator to wear the tool almost evenly over the engaging time of the tool, which contributes to a longer service life of the tool as well as a consistent and high surface quality of the workpiece to be machined.

According to the present invention, the machining apparatus, in particular a wide-belt sander for machining preferably panel-shaped workpieces consisting preferably at least in part of wood, wood material and/or synthetic, comprises a control device and at least a light signal display device which displays information on said machining apparatus in such a way that the information displayed by said light signal display device is visible to, or perceivable by, an operator. By means of the light signal display device, it is possible to visually display to the operator a wear condition of a tool of the machining apparatus and/or an advantageous insertion position of the workpiece to be machined in the machining apparatus as the information.

Thus, a light signal display device is provided, with which it is possible, for example in a wide-belt sander as a specific example of a machining apparatus, to visually display to the operator in a simple and safe way the wear condition of the abrasive belt or an advantageous insertion position of the workpiece to be machined. This is advantageous in particular for wide-belt sanders since, as already stated above, the handling of parts in wide-belt sanders used in the craft sector is in most cases completely up to the operator of the apparatus, and thus it is necessary that the operator distributes the parts to be machined evenly over the entire width of the wide-belt sander and over the complete engaging time of the abrasive belt to evenly wear the abrasive belt.

Here, the operator can be supported by the light signal display device according to the invention since it can visually display at any time to the operator in a simple and safe way the current wear condition of the abrasive belt and/or the advantageous insertion position of the workpiece currently being machined.

Thus, it is possible to distribute wear of the abrasive belt evenly over the entire width of the wide-belt sander and, thus, to increase the engaging time of the abrasive belt and to ensure a consistent surface quality of the workpieces to be machined.

Preferably, the machining apparatus comprises a conveyor, in particular a belt, chain or band conveyor adapted to move the workpiece to a machining apparatus and, optionally, to convey the workpiece out of the machining apparatus.

The light signal display device is preferably provided at an insertion area of the machining apparatus, at which the workpiece to be machined can be inserted into the machining apparatus and/or can be moved to the tool by a conveyor. The insertion area usually is a workpiece mount into which the workpiece can be inserted and at which a conveyor for moving the workpiece can be arranged. Preferably, the light signal display device is arranged in vertical direction above the insertion area. However, there is also the possibility to display the information on the insertion area, in particular above the insertion area.

Thus, it is possible to display to the operator of the machining apparatus in a simple and safe way directly on site, i.e. directly at the position where the operator has to insert the workpiece to be machined into the machining apparatus, the information about the wear condition of the tool and/or the advantageous insertion position of the current workpiece.

According to a preferred embodiment, a workpiece in an insertion area is taken by a conveyor such as a belt, band or chain conveyor and moved to a tool of the machining apparatus.

Furthermore, the light signal display device can be configured in the form of a display bar extending along, and in particular completely covering, the insertion area. However, there is also the possibility of displaying or projecting the information in such a way that it extends partially or completely along the insertion area. A display bar is understood to be a narrow, elongated display extending along the insertion area. Since the workpieces are usually inserted horizontally and evenly into the insertion area of the machining apparatus, it makes sense to also provide the display bar horizontally and, in particular, above the insertion area. Furthermore, it is advantageous if the display bar extends continuously from one side area to another side area of the insertion area, i.e. the display bar covers completely or substantially completely the insertion area. The light signal display device can also be formed by a plurality of display bars.

According to a further embodiment of the present invention, the light signal display device can display to the operator by different colors the wear condition of the tool and/or the advantageous insertion position of the workpiece to be machined. The display appears in particular by means of the colors green, yellow and red, with green being used for a good condition or a desired position, yellow for an average condition or a less desired position and red for a poor condition of the tool or a poor insertion position. It is also possible to use color gradients for better visualization.

Moreover, the control device preferably comprises a workpiece detection device by which length measurements of the workpiece and an insertion position of the workpiece in the insertion area of the machining apparatus can be detected, in particular even before insertion into the insertion area. The length measurements of the workpiece to be machined usually are the width and length of the workpiece. Furthermore, the insertion position is understood as that position of the workpiece, at which the operator of the machining apparatus has inserted the workpiece into the insertion area.

Thus, it is possible to display to the operator of the machining apparatus the advantageous insertion position of the current workpiece before insertion of the workpiece to be machined into the insertion area of the machining apparatus. This enables the operator to place the current workpiece directly in the advantageous insertion position in the machining apparatus, which renders an unnecessary repositioning or shifting of the workpiece obsolete.

Moreover, the control device is adapted to determine, over the engaging time of the tool, the wear condition of the tool and to display it to the operator by the light signal display device.

According to a further embodiment of the present invention, the control device determines the wear condition of the tool over the engaging time of the tool. The control device determines the wear condition by means of the detected length measurements of the machined workpieces and the respective insertion position thereof in the machining apparatus (position in the insertion area) as well as the respective machining parameters such as machining time, machining forces, grinding time, contact pressure, etc. This means that the control unit calculates the wear of the tool by said parameters, with recourse being made to empirically determined experience or simulated values for determination of wear, and the respectively determined wear is accumulated to determine a current wear condition. The determination of the wear condition will be discussed later in detail.

Moreover, the advantageous insertion position of the workpiece to be machined, which can be displayed to the operator by the light signal display device, can be determined by the control device and the determined wear condition of the tool as well as by the detected length measurements of the workpiece to be machined.

Preferably, there is also the possibility of configuring the control such that the advantageous insertion position is stochastically or chaotically determined. In other words, the insertion position is not determined based on the wear condition of the workpiece, but is stochastically or chaotically distributed over the tool surface over the engaging time of the workpiece and therefore, statistically speaking, the tool is evenly worn over the engaging time.

Moreover, the light signal display device can also comprise an inspection apparatus, by means of which a surface quality such as, for example, grain direction of the workpiece to be machined, can be determined and an advantageous insertion position and/or advantageous insertion orientation can be displayed to the operator by the light signal display device according to the determined surface quality.

Preferably, the light display device can be configured as a projection unit, in particular in the form of a projector.

According to a further embodiment of the present invention, the light display device is configured as LED bar, OLED bar and the like, and a resolution, i.e. the distance between individual display elements or display sections of the light display device or the arrangement of the display sections at the projected area, is less than 5 cm, in particular less than 2 cm. Preferably, the light display device is configured by a band having spaced LEDs, the resolution corresponding to the distance between the individual LEDs (display elements). Furthermore, the light display device preferably has a 24-bit resolution, with which the color gradients can be displayed.

Furthermore, the at least one tool (WZ) of the machining apparatus can be an abrasive belt, an abrasive roller, a polishing roller, a disk brush or the like. If there are plural tools, these can comprise one of said tools. Should there be plural tools, it is further preferred that different tools of said tools are combined, for example one or more calibrating roller(s), one or more abrasive belt(s), one or more polishing roller(s), one or more disk brush(es).

Moreover, the present invention relates to a method for operating a machining apparatus, in particular the above-described machining apparatus, said method comprising: determining the wear condition of the tool, displaying the determined wear condition of the tool by means of a light signal display device and/or displaying an advantageous insertion position of the workpiece to be machined in the machining apparatus by the light signal display device, with in particular the advantageous insertion position being determined based on the determined wear condition of the tool or being stochastically or chaotically determined.

According to a preferred embodiment of the present invention, the above-described method further comprises: detecting length measurements of the workpiece to be machined, detecting the insertion position of the workpiece to be machined in an insertion area of the machining apparatus, checking whether a wear condition of the tool has already been determined, if

-   -   yes, displaying the wear condition by the light signal display         device,     -   no, displaying, by the light signal display device, a wear         condition corresponding to the condition of a new tool,         determination of wear of the tool based on the detected length         measurements, the detected insertion position and present         machining parameters such as, for example, machining time,         machining forces, grinding time, contact pressure, etc.,         determination of a current wear condition by accumulating a         given wear condition and the determined wear, and storing the         determined current wear condition.

Moreover, by means of the method, the current wear condition of the tool can be determined over the engaging time of the tool based on an accumulation of determined wear of the tool, with the respective wear of the tool having in each case been determined at the time when a new workpiece was inserted into the insertion area of the machining apparatus.

Preferably, the method further comprises: detecting the length measurements of the workpiece to be machined before insertion of the workpiece to be machined into the insertion area, checking the current wear condition of the tool, determining the advantageous insertion position based on the current wear condition of the tool and the detected length measurements of the workpiece to be machined, and displaying the advantageous insertion position by the light signal display device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic perspective illustration of an embodiment of the machining apparatus according to the present invention,

FIGS. 2a-2c show different examples of display possibilities by means of the light signal display device according to one embodiment of the present invention, and

FIG. 3 shows a flow chart presenting the individual steps of one embodiment of the method for operating a machining apparatus according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, preferred embodiments of the present invention will be explained with reference to the accompanying drawings. Further variants and modifications of individual features cited in this context can each be combined with one another to form new embodiments.

FIG. 1 shows a schematic perspective view of one embodiment of the machining apparatus according to the present invention.

As can be seen in FIG. 1, a machining apparatus 2 comprises, according to one embodiment of the present invention, at least one light signal display device 10 provided at machining apparatus 2 in such a way that it is easily perceptible by an operator of machining apparatus 2. To be easily perceptible to the operator, light signal display device 10, as is shown, is preferably disposed in the vertical direction above an insertion area 4 of machining apparatus 2. Thus, during the insertion procedure of a workpiece W to be machined into insertion area 4, light signal display device 10 is directly visible to the operator and thus is easily perceptible. However, there is also the possibility to provide the light signal display device not directly at insertion area 4, but to project the information, thus, for example, the degree of wear of tool WZ or the advantageous insertion position, to machining apparatus 2, in particular close to insertion area 4.

It can further be taken from FIG. 1 that light signal display device 10 is preferably configured in the form of a display bar 11 extending completely along insertion area 4 in the embodiment shown, i.e., as is shown, from a right side region of insertion area 4 up to a left side region of insertion area 4. Due to the fact that light signal display device 10 extends completely along insertion area 4, it is ensured that light signal display device 10 covers the entire length of tool WZ.

In FIG. 1, a wide-belt sander 2 is shown as a specific example of a machining apparatus 2. Accordingly, light signal display device 10 covers the entire length of the abrasive belt of wide-belt sander 2 in the embodiment shown. Accordingly, it is possible to display to an operator by light signal display device 10 a wear condition of the abrasive belt over the entire length of the abrasive belt. It is equally possible to display by light signal display device 10 to the operator of wide-belt sander 2 an advantageous insertion position EP_(v) of a workpiece to be machined W with regard to insertion area 4.

As is indicated in FIG. 1 and is further illustrated in FIGS. 2a to 2 c, the determined wear condition of tool WZ and/or the advantageous insertion position EP_(v) are displayed to the operator by means of different colors in the proposed light signal display device 10. To configure light signal display device 10 in a self-explanatory way, preferably the known colors green (G), yellow (Y) and red (R) are used (FIG. 2a ).

It can be derived from FIG. 2b that there is also the possibility to form the light signal display device 10 by means of two or more display bars 11 preferably disposed on top of each other. Accordingly, it is possible to indicate to the operator the advantageous insertion position EP_(v) by top display bar OL and, at the same time, to indicate to the operator the wear condition of tool WZ by lower display bar UL. The individual display bars 11 are in turn preferably formed of a plurality of LED rows, the individual rows extending along insertion area 4.

As can moreover be taken from FIG. 2 c, it is also possible by light signal display device 10 to display to the operator urgent or important information such as, for example, malfunction and the like of machining apparatus 2, by which the operability of machining apparatus 2 is enhanced. It is also possible thereby, inter alia, to indicate recommendations, status information and the like to the operator.

Reverting to FIG. 1, it can also be taken therefrom that machining apparatus 2 has a control device 2 and a workpiece detection device 30. By means of workpiece detection device 30, which in the embodiment shown is arranged on the outside of machining apparatus 2 such that it can monitor the entire insertion area 4, it is possible to detect insertion position EP of a workpiece W inserted by the operator into insertion area 4. Furthermore, it is preferred that workpiece detection device 30 is configured such that it cannot just monitor insertion area 4, but is also capable of monitoring an area in front of insertion area 4. This allows early detection of a workpiece W to be machined so that the advantageous insertion position EP_(v) can be indicated to the operator even before insertion of workpiece W into insertion area 4.

In the embodiment of the present invention shown in FIG. 1, workpiece detection device 30 is configured in the form of an optical detection device, in particular a camera. However, inductive sensors, ultrasonic sensors and optical sensors can also be used. As is shown, workpiece detection device 30 can moreover comprise not only one camera, but can also be provided with a plurality of cameras and/or a plurality of different sensors, if necessary.

The use of a camera offers the advantage that, if desired, a surface quality of workpiece W, such as, for example, grain direction, can be detected. In this case, the camera is also a component of inspection apparatus 40. Further information (data) such as, for example, workpiece type, workpiece number and the like can be determined in advance by the workpiece detection device.

FIG. 3 shows a flow chart presenting the individual steps of an embodiment of the method for operating a machining apparatus 2 according to the present invention.

In step 1 of the method for operating a machining apparatus 2, length measurements X, Y of workpiece W are detected by workpiece detection device 30 and entered into control device 20.

In method step 2, an insertion position EP of the workpiece to be machined is detected by sensors in machining apparatus 2, in particular in insertion area 4 and/or by workpiece detection device 30.

It is checked by method step 3 whether wear condition data is already available, i.e. whether a workpiece W was already inserted and machined in advance, and workpiece WZ has therefore already become partially worn. If yes, the method is continued with step 4. If no wear condition data is available, the method is continued with step 4a.

In method step 4, the present wear condition of workpiece WZ is displayed to the operator by light signal display device 10, which gives the operator the opportunity to optimally insert workpiece W into the machining apparatus 2 such that workpiece WZ will be uniformly used, and thus worn, over the entire engaging time. In method step 4, it is also possible to display to the operator an advantageous insertion position EP_(v) of workpiece W.

In parallel method step 4a, it is displayed to operator 10 by light signal display device 10 that no wear condition data is available. This means that tool WZ usually is a new tool WZ, for which a wear condition has not yet been determined. In general, this is signaled by an entirely green flashing light signal display device, which means that no wear is found on tool WZ.

The two alternative method steps 4 and 4a are followed by step 5, in which a present wear condition is determined. The wear condition is an accumulation of individual wear of tool WZ, with each being determined during machining of a workpiece W. Wear is determined based on the detected length parameters X, Y and the detected insertion position EP as well as the given machining parameters. Based on length measurements X, Y and detected insertion position EP, it can be determined which specific area of tool WZ is stressed by the machining performed and is thus worn. Moreover, the respective load and wear of tool WZ can be determined based on the available machining parameters such as, for example, machining time, machining forces, grinding time, contact pressure, etc. In summary, it can be specifically determined which area of the tool WZ is worn to what extent.

It is thereby also possible to determine an overall wear in a machine with several aggregates (with different tools WZ). There is thus the possibility that certain grinding aggregates are disengaged during machining of a certain workpiece W, for example one of the grinding devices mentioned hereinafter: one or more calibrating rollers (steel roller or rubberized roller and/or a fine grinding aggregate (cross-belt and H-aggregate). Hence, a common total wear is determined across several different tools and a total wear condition and/or an advantageous insertion position EP_(V), which takes the total wear condition into account, is accordingly displayed to the operator by light signal display device 10.

It is also possible to display the degree of wear of individual grinding aggregates.

Furthermore, it is also possible in a machining apparatus 2 having several aggregates, such as for example in a wide-belt sander with four aggregates, to provide a separate light display device, in particular an LED bar, for each aggregate. The four aggregates can, for example, be two calibrating rollers and two abrasive belts (pre- and fine grinding). Thus, there is the possibility to display to the operator a degree of wear and an advantageous insertion position EP_(v) determined for each individual aggregate.

For example, in the first place, the wear condition of all aggregates can be displayed separately to the operator at the same time. If the operation mode is switched on and/or a workpiece is inserted which, for example, is to be machined by three aggregates, it is possible to display to the operator a total wear and an advantageous insertion position EP_(V) by taking the degrees of wear of all three aggregates into account. To this end, the degrees of wear of the three aggregates are offset against each other and a total value is formed.

However, there is also the possibility to display all three degrees of wear separately to the operator, and it is up to the operator where he eventually inserts the workpiece.

It is further possible to realize the same function by only one light display device. In this case, individual horizontal lines of the light display device, in particular the LED bar, would display the different degrees of wear.

Next, in step 6, the determined current wear condition of tool W of machining apparatus 2 is stored in a database such that recourse is possible to this wear condition during a subsequent machining of a new workpiece W. With step 6, the method for operating a machining apparatus 2 is completed and machining apparatus 2 returns to the starting position (step 1). 

1. A machining apparatus comprising: a control device; and at least one light signal display device which displays information on the machining apparatus such that the information displayed by the light signal display device is visible to an operator, wherein the control device is configured to control the light signal display device such that a wear condition of at least one tool of the machining apparatus or an advantageous insertion position of a workpiece to be machined is displayed as information to the operator.
 2. The machining apparatus according to claim 1, wherein the light signal display device is provided at an insertion area of the machining apparatus, at which the workpiece to be machined can be inserted or is movable toward the tool by a conveyor, or the light signal display device displays the information on the insertion area.
 3. The machining apparatus according to claim 2, wherein the light signal display device is configured in the form of a display bar extending partially or completely along the insertion area, or wherein the information is displayed such that it extends partially or completely along the insertion area.
 4. The machining apparatus according to claim 1, wherein the light signal display device can display to the operator by different colors the wear condition of the tool or the advantageous insertion position of the workpiece to be machined, by the colors green, yellow and red, and wherein green is used for a good condition or a desired position, yellow for an average condition or a less desired position and red for a poor condition or an undesired position.
 5. The machining apparatus according to claim 2, further comprising a workpiece detection device, by means of which length measurements of the workpiece and an insertion position of the workpiece in the insertion area of the machining apparatus can be detected.
 6. The machining apparatus according to claim 5, wherein the control device is configured to determine by an engaging time of the tool the wear condition of the tool, and to display it to the operator by controlling the light signal display device.
 7. The machining apparatus according to claim 6, wherein the control device determines over the engaging time of the tool the wear condition of the tool by means of the detected length measurements of the machined workpieces and the respective insertion position thereof in the machining apparatus as well as by respective machining parameters.
 8. The machining apparatus according to claim 5, wherein the control device is configured to determine, by means of a determined wear condition of the tool and by the detected length measurements of the workpiece to be machined, the advantageous insertion position of the workpiece to be machined and to display it to the operator by the light signal display device.
 9. The machining apparatus according to claim 1, wherein the control device is configured to stochastically or chaotically determine the advantageous insertion position.
 10. The machining apparatus according to claim 1, wherein furthermore an inspection apparatus is provided adapted to determine a surface condition, such as grain direction, of the workpiece to be machined and to display to the operator, according to the determined surface condition, an advantageous insertion position and/or advantageous insertion orientation by the light signal display device.
 11. The machining apparatus according to claim 1, wherein the light display device is configured as a projection unit.
 12. The machining apparatus according to claim 1, wherein the light display device is configured as an LED bar, or an OLED bar.
 13. The machining apparatus according to claim 1, wherein the at least one tool is an abrasive belt, an abrasive roller, a polishing roller, or a disk brush.
 14. A method for operating a machining apparatus according to claim 1, the method comprising: determining the wear condition of a tool of the machining apparatus; displaying the determined wear condition of the tool by a light signal display device and; displaying an advantageous insertion position of the workpiece to be machined in the machining apparatus by the light signal display device.
 15. The method according to claim 14, the method further comprising: detecting length measurements of the workpiece to be machined; detecting the insertion position of the workpiece to be machined in an insertion area of the machining apparatus; checking whether a wear condition of the tool was already determined; determining wear of the tool based on the detected length measurements of the detected insertion position and given machining parameters; determining a current wear condition by accumulating a current wear condition and the determined wear; and storing the determined current wear condition.
 16. The method according to claim 15, wherein over an engaging time of the tool the current wear condition of the tool is determined based on an accumulation of determined wear of the tool.
 17. The method according to claim 15, the method further comprising: detecting the length measurements of the workpiece to be machined before insertion of the workpiece to be machined into the insertion area; checking the current wear condition of the tool; determining the advantageous insertion position based on the current wear condition of the tool and the detected length measurements of the workpiece to be machined; and displaying the advantageous insertion position by means of the light signal display device.
 18. A method comprising: using least one light signal display device mounted to the machining apparatus according to claim 1; or displaying thereon information to display to an operator a wear condition of at least one tool of the machining apparatus or an advantageous insertion position of a workpiece to be machined.
 19. The machining apparatus according to claim 1, wherein the machining apparatus is a wide-belt sander.
 20. The machining apparatus according to claim 1, wherein the machining apparatus is for machining panel-shaped workpieces.
 21. The machining apparatus according to claim 20, wherein the panel-shaped workpieces consist at least in part of wood, wood material or synthetic.
 22. The machining apparatus according to claim 2, wherein the light signal display device is disposed in the vertical direction above the insertion area or displays the information at this position.
 23. The machining apparatus according to claim 4, wherein color gradients can be used for the display.
 24. The machining apparatus according to claim 5, wherein the length measurements of the workpiece and the insertion position of the workpiece in the insertion area of the machining apparatus can be determined even before insertion into the insertion area.
 25. The machining apparatus according to claim 7, wherein the respective parameters comprise at least one of machining time, machining forces, grinding time or contact pressure.
 26. The machining apparatus according to claim 11, wherein the projection unit comprises a projector.
 27. The machining apparatus according to claim 12, wherein a resolution of the light display device is less than 5 cm.
 28. The machining apparatus according to claim 27, wherein the resolution of the light display device is less than 2 cm.
 29. The method according to claim 14, wherein the advantageous insertion position based on the determined wear condition of the tool is stochastically or chaotically determined. 